Lechuguilla Cave has been completely isolated from the outside world for over four million years, making it one of the world's most pristine ecosystems. And yet it's full of bacteria that are resistant to modern antibiotics. This is fantastic news.

Part of New Mexico's Carlsbad Caverns, the cave was cut off from the rest of the world millions of years ago thanks to a thick layer of rock all around it. Only water could wend its way through the rock, and the path to the cave is so ridiculously tiny and circuitous that it takes ten thousand years to reach the cave itself. That means no new lifeforms had reached the cave until an entrance was first uncovered in 1984.

That's why the discovery of antibiotic-resistant bacteria inside the cave is so shocking. It's not just the fact that the bacterial strains in this cave evolved isolated from modern medicine — they are about twenty times older than the human race. The good news is that Lechuguilla Cave isn't some sort of bacterial time bomb — none of the strains found in the cave could cause disease in humans. They are superbugs in terms of their natural resistance to antibiotics, not their capacity for disease.

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So yeah, that's good news, but why is this discovery great news? Well, this antibiotic resistance must have evolved for some reason, and the most obvious explanation is that the bacteria actually encountered naturally occurring antibiotics — possibly produced by the bacteria themselves as they competed with nearby microbes — and had to fight them off, as McMaster University researcher Gerry Wright observes:

"Our study shows that antibiotic resistance is hard-wired into bacteria, it could be billions of years old, but we have only been trying to understand it for the last 70 years. This has important clinical implications. It suggests that there are far more antibiotics in the environment, that could be found and used to treat currently untreatable infections."

The researchers say that, between all the different bacterial strains found in the cave, they were able to identify pretty much every form of antibiotic resistance known to medical science. What's more, one strain showed signs of a form of antibiotic resistance that hasn't emerged yet in a clinical setting. Since that particular strain is a distant relative of the anthrax bacterium, it's nice to have early warning of this potential threat, and this discovery gives time for clinicians to prepare for it.

The finding also demonstrates just how widespread antibiotic resistance is among bacteria, and that the emergence of such resistance is down to more than just poor human management of these drugs, which includes overuse of antibiotics on farms and patients not completely the entire course of prescribed antibiotics. The researchers found most of the bacteria were resistant to at least one antibiotic, and several were resistant to over a dozen antibiotics.

That fact could help explain just why superbugs have been able to emerge so fast in hospitals and farms, the two places where antibiotics are most heavily used. It's not simply a case of supercharged evolution — multiple studies suggest these disease-causing superbugs would need thousands, maybe even million of years to emerge without help.

In this case, the help comes from all the otherwise harmless bacteria in the environment. While these bacteria don't cause disease, each carries a slightly different form of antibiotic resistance, which may have evolved millions or billions of years ago. The deadly bacteria can exchange genes with the resistant bacteria and pick up the tools needed to overcome the antibiotics that would otherwise wipe them out.

While this discovery holds some big implications and could be of tremendous use to medicine, we only have half the picture until we find those naturally occurring antibiotics. We might find them in the cave itself, or it's possible the secrets will be hidden somewhere in these bacteria's DNA. Until then, we can at least proceed with the knowledge that antibiotic resistance is a problem far more ancient than we initially suspected, and hope that equally ancient solutions might soon emerge.